Modulation system



' April 10, 1928. 1,665,350

F. GERTH MODULATION SYSTEM Filed June 8. 1927 Jive/21 01". 5/0 69/77?Patented Apr. 10, 192a.

'rnLix' GERTH, or BERLiui'rnMrELiior, GERMANY, AssIeiion-ro ojlnort nnzAK'rrE L I vensnnnscnar'r, or BERLIIFTEMIELHQF, ensarty.

, MODULATION sYs'r'n u.

f Application meanne- 2s, 1927,'s;riai No. aoaosa mi'in Gamay July 5,1926'. v

- The" present invention has reference 1 to high frequency generatingsystems'tor radio communication purposes comprisinga -liigli frequencyalternator supplying a fundamen- -'tal frequency and one or moreironcoi'ed frequency transformers'to raise said fun- -'dan'ientalfrequency to a higher operating frequency. In such avsystein it hasbecome known to use an iron-cored auxiliary magnetized choke coil formodulating vthe high frequency currents to he radiated in the form ofelectric waves into space, in accordance with signals or speech to betransmitted." 'The iron-cored choke modulator to this end is insertedinto a circuit cari'ying acter in question, in that beat phenomenacaused by conditions of instability] may occur between the frequencytransformer output circuit and a following load (intermediary orantenna) circuit givingi'ise to very undesired disturbances.

It is the object of the present overcome these inconveniences to whichend a special independent resonant circuit is provided coupled in anyknown manner to the output (antenna) or a preceding circuit and whichcontains the modulator choke coil.

My invention is illustrated by means of example by thef accompanyingdrawing which maybe referred to in connection with the followingdetailed disclosure in order to get a clear and precise statement.of'its exact features and working.

Referring to the drawing, the. reference v numeral 1 designates a highfrequency alteriiator working in a well-known manner upon a circuit(fundamental frequency circuit) comprising a selfeinduction coil. 2, acapacity 3 and the winding 4 of an iron-cored high-frequency transformer5. The output circuit of the frequency transformer is con-' stituted bya capacity 6, tuning'coil 7, cou- .pling coil 8 and is tuned to andcarries a frequency. being a multiple of the transformer input(alternator) frequency. Coupled to the transformer output or multi-.pli'cation circuit, as it is called too, is an intermediary circuitconstituted by a capacinvention to ity 9; tunii'ig coil 10',and-ceupling;coils 111 and12. I Electric oscillations are'ti'ansferredfrom the intermediary circuit to the radiating;

by a fractional part only ofthe peak value of the fundamental(alternator) current. The self induction 2; of the fundamentalvtransformer 5 isdiinenSiOned tobe saturated frequency circuit is givensuch a value with respect to the capacity 3, that virtue-of thesaturation of thecore and the corresponding alteration of its magneticpermea bility the tuning vofthe fundamental circuit periodically changedfrom a condition of resonance to a condition ofnon-resonance (criticalresonance). The magnetic flux of the core changes suddenly eachhalf-cycle from its positive to its negative saturation value. Short.tension peaks are periodically generated at the terminals of jthetransformer winding and-follow each other at regular intervals whichproduce byshock vexitati'on damped wave trains of'the natural frequencyof the secondary circuit 4:, 6;8, 7

(erg. 13fold the fundamental frequency).

By virtue of the regularly occuringimpulses quicklyfollowing each othera practically undamped wave is produced. 'However,. 1n

the case of an iron-cored"modulatorcoil bewe inserted in theantennmorapreceding circuit, conditions of instability duringthe operaton of thechoke coil may ar'ise giving rise to beat phenomena between two suchcircuits resulting specially in disturbing sing- "111g noises. The chiefreason for that consists inthat by reaction of the circuit containingthe choke coil upon the transformer secondary (multiplication) circuitconditions in the saturation oflthe transformer "iron-coreare altered ina-manner to introduce conditions of instability in the system.

This may occur during the adjusting of the choke coilrespectivelyitsflcorrect auxiliary current as well as during operation when alteringits effective i'esistanc'ein accordance with signals to. be transmittedby" controlling its D. Gunagnetwrng current: These drawbacks are avoidedor at least minimized to a practically sufficientdegree according to,this inventionby inserting the circuit and consisting of a variablecapacity modulator. choke coil 17 into a special independent circuitcoupled with the antenna 19 and a coupling coil 18 coupled with theantenna self-inductance l5.vv 20 designates thefhigh-frequency windingof the choke dev ce, 21 its D. C. controlling winding con nected to amicrophOneQZ-B in series with a J What I claim is:

r 1. A radio transmission system of the character described(comprisingin combina- ,tion a circuit carryinga fundamental frequency; aniron-cored high-frequency trans-- 'formerfor raising said fundamentalfrequency to a useful higher operating frc v quency, a load or antennacircuit being in L insformer o utoperative relation with the 'putcircuit and an auxiliary resonant circuit 'beingin coupling relationshipwith a circuit carrying high-frequency currents and containingv aniron-cored auxiliary magnetized choke device for modulating the highfrequency currents in 'accordancefwith signals to jbe' transmitted. l 3j '2. 'A radio transmission system of the character described comprisingin combina-* tion a high-frequency alternator generating currents of afundamental frequency, an iron-cored high frequency transformer suppliedby said alternator and carrying in'its output circuit currents'of afrequency being a multiple of said fundamental frequency, an antennaload circuit being inoperative cuit and an iron-cored choke deviceinserted into a resonant circuit being in coupling relation with saidtransformer output" cir' FELIXGERTH, I

